Natural food represents the single food source for fish and prawn in traditionalestuarine pond (tambak) in Pengaradan Countryside of Tanjung District of Brebes Regency.The prawn production among estuarine pond varies between < 125 ind/ha, 150 – 200 ind/ha,and 250 – 300 ind/ha per period of crop (3,5 – 4 month). This might be due to theoccurrence of natural food in the pond. One of natural food of prawn is Polychaeta. The aimof the research is to find out the diversity, density, and biomass of Polychaeta in the pondwith different production level. The research was conducted during June – August 2004. Asurvey was done by stratified random sampling. Research location is divided into threestations according to level of prawn production of the pond. Station I, II, and III represent pond with the highest, moderate, and low prawn production respectively. The sample sizewas 5% of total pond in each station. Sample was collected by using core sampler 12,5 cmin diameter. Data was analyzed by using index of diversity, F test, and 50% rule. The resultshows that there are two species in the estuarine pond area studied including

Nereis

spp and

Platynereis

spp. Density of Polychaeta at stations I, II, and III was 118, 61, and 31 ind/m

3

respectively. Biomass of Polychaeta at station I, II, and III was 43,26; 17,59; and 10 g/m

3

respectively. The higher the prawn production of the pond is the higher the density and the biomass of Polychaeta. Density and biomass in station I and II was highly significantlydifferent from that in station I and III. According to 50% rule, the density and biomass of station I was different from that of station II, and that of station I and III.